I am planning on building a motor, and I was just wondering how do you figure what the redline is gonna be? :confused: Any help is appreciated! graemlins/thumbsup.gif

Need more info here.
Cast crank or forged ?
After market rod bolts? Valve spring/camshaft package?
What cylinder heads?
What kind of engine?
How many cubic inches?

cam,heads, intake and carb mostly,,,then crank,rods,balanced or not....heck 6000 is enough

Here are two things that are considerations. Piston speed and/or valve float. With the right springs, piston speed is the major factor.

Here is some info:

Formulas:

Average Piston Speed = Stroke * rpm / 6

By the way, the usual limit of engine speed based on the stress of the
reciprocating components is not RPM, it's piston speed.

The formula is: P = S × R ÷ 6 where "P" is piston speed in feet per minute, "S" is the stroke in inches, "R" is engine RPM, and 6 is a constant. About 4,000 f/m is safe for good-quality
cast pistons and up to 5,000 f/m for forgings, for peak power only - shifting,
not cruising!

Since this speed is not constant throughout the engine's rotation,
piston speed is only an average. A better method of calculating maximum RPM is
based on the point of fastest piston acceleration, and takes into account the
rod length (longer rods improve the safe RPM slightly).

The formula is:

Z = N2 × S (1 + (1 ÷ 2n)) ÷ 2189

where "Z" is piston acceleration in feet per second, per
second, "N" is engine RPM, "S" is the stroke length in inches, "n" is the
rod-to-stroke ratio, and 2189 is a constant. A safe limit
for "Z" is about 100,000 f/s2, although this will cause ring flutter with 1/16"
compression rings.I'll leave it to you to struggle through the math smile.gif .

Thanks for the help! graemlins/thumbsup.gif I havent decided exactly what parts Im going to use yet, but at least I have a formula. I still need to find a 4 bolt big block if anybody knows of where there is one for sale.

Pat

The formula is:
Z = N2 Å~ S (1 + (1 ÷ 2n)) ÷ 2189

should that be n^2 instead of n2?
I can't get that formula to work, but I found this one and I think the math is easier and I get 96500 @ 7000rpm instead of 84 :D
Gmax = ((N^2 x L)/2189) x (1 + 1/(2A))
Gmax is maximum piston acceleration, in feet per second squared
N is crankshaft speed, in RPM
L is stroke, in inches
A is the ratio of connecting rod length, between centers, to stroke

am I right or was I following the steps wrong with the first formula?

I hate to admit it but I never tried the formula. It was posted on Chevy Talk and I saved it for future use.